When built-in sinks made of a plastic composite material are referred to in this application, these are to be understood not only as sinks cast from a casting resin filled with plastic particles or, for example, formed or pressed from a glass-fiber reinforced plastic, but quite generally as sinks made from a material containing in addition to plastic as matrix material or binder, some fillers or other and/or reinforcement materials and possibly also being in the form of a laminate.
The support formed by the work top or cover plate can be a surface zone of this plate adjoining the opening cut out of it, or also the horizontal area of a step adjoining the opening cut out of the plate and machined from above in the plate, or the lower flank of a groove machined in the circumferential surface of the opening cut out of the plate. The supporting surface of the built-in sink will usually be the horizontal underside of a radially outer rim area of the built-in sink.
Securing elements of the kind described at the outset are known, as is a securing device of the generic kind defined hereinabove. The main body of such a securing element does not necessarily have to consist of one piece. In principle, it could also be comprised of several parts, for example, a nut forming the thread for the clamping screw and a carrier, for example, in the form of a punched and bent part having the shape of a lying U for holding the nut.
The cover plate will usually be the cover plate of a bottom cupboard of a built-in kitchen, however, the cover plate could also be formed by any other kind of plate in which the built-in sink is to be secured.
In a known device of the kind mentioned at the outset for securing a built-in sink cast from a casting resin containing filler particles, several protuberances are formed on the built-in sink below the supporting surface and in the circumferential area of its underside. These are spaced from one another in the circumferential direction of the built-in sink, lie within the opening cut out of the plate, i.e., do not project downwardly over the cover plate, and have outer surfaces located opposite the circumferential surface of the cut-out opening which form a downwardly opening acute angle with the circumferential surface of the cut-out opening. Attached to these outer surfaces of the protuberances are the main bodies of the securing elements, more particularly, by means of screws, for which blind holes, whether it be threadless blind holes into which self-tapping screws are screwed or threaded bores, have been previously drilled in the protuberances. This way of joining the securing elements to the built-in sink has quite a number of disadvantages. In this regard, the making of the blind holes which have to be precisely positioned results in a considerable increase in costs, as does the tightening of at least two fastening screws per securing element. Furthermore, there is the danger that the plastic material of the built-in sink will fracture and break open in the area of the blind holes on the used and visible side of the sink if the tap drill or the self-tapping screw pushes chips or the like ahead of it and presses them together at the bottom of the blind hole when the thread is being made.
An object of the present invention is to provide a more economical way of attaching the securing elements to a built-in sink made of a plastic composite material.
The inventive solution to this problem originates from the consideration that built-in sinks made of a plastic composite material require finishing on a milling machine, above all, in the region of the sink rim. At that time, however, while the sink is set up for this purpose, horizontal slots, i.e. extending parallel to the supporting surface of the built-in sink, or even a continuous circumferential slot can be milled in an extremely economical way with the milling machine at the places in the built-in sink where the securing elements are to be attached, and so only the main body of the securing elements has to be provided with a projection which is fittingly insertable, preferably with a press fit, into such a slot and thus holds the pertinent securing element on the built-in sink. Accordingly, an inventive device of the kind described at the outset is characterized by a slot extending at least approximately parallel to the cover plate being provided in an underside area of the built-in sink located opposite the circumferential surface of the opening cut out of the cover plate, and the main body of the securing element having a projection for insertion in this slot and thereby holding the securing element on the built-in sink.
The inventive securing device first results in the drilling operation which has to be carried out with an additional device and also the operation of screwing-in the fastening screws being dispensed with, which allows the manufacturing costs to be reduced. Furthermore, during the milling of the slot or slots and the attachment of the securing elements to the sink, there is no danger of the visible side of the built-in sink being damaged. Finally, there is no problem with positioning the slot or slots precisely, as the milling of the slots can be carried out while the sink is set up in the milling machine for the operation of finishing the sink rim, as explained hereinabove.
Depending on the design of the main body of the securing elements (the projection to be inserted into the slot could, for example, be connected to the main body via a web or the like extending upwardly from the actual main body), the main body of the securing elements does not necessarily have to be arranged in the space between the circumferential surface of the opening cut out of the cover plate and the underside of the built-in sink. Embodiments of the securing element in which the main body protrudes into this space and has a supporting area adapted to lie against the circumferential surface of the cut-out opening are, however, recommended. As that area of the clamping member which during the tightening of the clamping screw is supported on the cover plate lies on the side of the securing element facing away from the aforementioned projection and the slot, respectively, viewed in the vertical direction, the projection tends to slide out of the slot during the tightening of the clamping screw and the pressing of the clamping member against the cover plate. However, this can be avoided in such embodiments by the main body being supported by the circumferential surface of the cut-out opening, more particularly, in a position in which its projection at least still protrudes into the slot. Such support is particularly effective when the supporting area of the main body is located approximately opposite its projection, viewed in the horizontal direction.
The projection could have the shape of a tongue or several tongues arranged in spaced relation to one another in the circumferential direction of the opening cut out of the plate. However, greater stability is obtained when the projection is in the form of quite a long (measured in the longitudinal direction of the slot) web, and embodiments are preferred in which the length of the web is at least approximately equal to the width (again measured in the longitudinal direction of the slot) of the clamping member so that there is located opposite each point of the clamping element supported on the cover plate a point on the web through which the reaction forces can be introduced into the sink body.
As mentioned hereinabove, the main body could, for example, be in the form of a punched metallic bent part. However, since such securing elements are always manufactured in large numbers, favorable manufacturing costs are achievable by the main body including the projection being produced in an injection molding process and, in particular, formed by a plastic injection molded part. This measure also makes it possible to provide in an extremely economical way means for effectively preventing the projection on the main body of the securing element from being pulled out of the sink slot. For this purpose, it is proposed that the projection be provided with at least one elevation for counteracting the pulling of the projection out of the slot, and, in particular, that there be formed on the projection in the form of a web at least one lamina forming one such elevation which extends away from the web, more particularly, obliquely in the direction of withdrawal of the web from the sink slot so that the lamina becomes jammed between web and adjacent slot wall when an attempt is made to pull the web out of the sink slot.
As is customary with sink securing elements, in preferred embodiments of the securing element, its clamping screw extends through an opening in the clamping member and lies with its screw head from below against the clamping member. In order that the clamping member cannot turn along with the clamping screw when it is being turned, before the clamping member is pressed against the cover plate, it is recommended that the main body be designed so as to form for the clamping member at least one slide or guide surface extending in the longitudinal direction of the screw and acting as means for preventing turning.
As will be evident from the following, the invention makes it possible, without any additional cost, for the sink to be secured either with a clamping member which engages under the cover plate in the known way or with a clamping member which is designed in the known way as a spreading part for support on the circumferential surface of the cutout opening. Accordingly, preferred embodiments of the invention are characterized by the main body being selectively combinable with a clamping member designed as an under-engaging part for engaging under the cover plate or as a spreading part adapted to be supported on the circumferential surface of the cut-out opening. This results in a further reduction of costs if there is a market for both types of fastening.
If each of the slots is substantially longer than the projection of the associated securing element or if the built-in sink is provided with a continuous circumferential slot, the invention offers a further important advantage. In particular with plastic sinks, it is sometimes the case, depending on the manufacturing process, that not all of the areas of the supporting surface of the built-in sink with which it rests on the cover plate lie in a common plane. However, with longer slots or a continuous slot, the invention makes it possible, by appropriate placing of the securing elements, for the sink rim to be pulled downwards with the aid of the securing elements at those points where it would otherwise lie somewhat higher. This is highly advantageous, particularly for so-called flush mounting of the sink (with flush mounting, the highest areas of the sink lie at the level of the upper side of the cover plate).